People with severe speech impairments who use text-based augmentative and alternative communication (AAC) systems are forced to make less than optimal choices when delivering messages, resulting in communication that is flawed with respect to either the speed of message delivery or the appropriateness of message content. These choices involve a violation of one conversational rule to satisfy another. AAC system users have no guidance.in determining which of these trade-offs might be viewed more favorably by the general public. A theory, therefore, has been developed that identifies the effects of trade- offs between selected conversational rules, as well as the relative value of these rules, on attitudes of public service providers toward adult AAC users and their communication, such that choices leading to the most and least favorable assessments can be determined. The specific aim of this project is to test this theory of conversational trade-offs in AAC. This will be accomplished first by systematically exploring the effects of trade-offs between the rule pertaining to speed of message delivery and each of those pertaining to the appropriateness of message content with respect to informativeness (Experiment 1), relevance (Experiment 2), and redundancy (Experiment 3). This will provide a partial ordering of the rules when speed is one of the rules involved. Experiment 4 will then compare the effects of violations of informativeness, relevance, and redundancy to complete the goal of confirming the predicted hierarchy of these rules. A theory that explains and predicts outcomes of choices such as these would contribute to an understanding of AAC and of ways to optimize the success of AAC system users. This knowledge will guide clinicians in directing users in the selection of choices that yield the most positive evaluations by public service providers who can significantly contribute to the AAC system user's successful inclusion in society. This knowledge will also provide direction for future systems development. Although these choices most obviously apply to AAC, it is likely that people with other types of communicative disorders may encounter similar choices. The long-term goal of this research proposal, then, is to test the application of this theory as it relates to various subpopulations of AAC system users and other populations of atypical speakers in order to better understand the outcomes of flawed communication resulting from violations of conversational rules, and to use the results to develop appropriate technologies for aiding such populations. Schneider, jay W.